The present invention relates to data storage systems, and more particularly, this invention relates to conductive polymers which may be particularly useful for magnetic recording media.
In magnetic storage systems, magnetic transducers read data from, and write data onto, magnetic recording media. Data is written on the magnetic recording media by moving a magnetic recording transducer to a position over the media where the data is to be stored. The magnetic recording transducer then generates a magnetic field, which encodes the data into the magnetic media. Data is read from the media by similarly positioning the magnetic read transducer and then sensing the magnetic field of the magnetic media. Read and write operations may be independently synchronized with the movement of the media to ensure that the data can be read from and written to the desired location on the media.
In a magnetic tape drive system, a magnetic tape, which includes a plurality of laterally positioned data tacks extending along the length of the tape, is drawn across the magnetic head (i.e., the magnetic read/write transducer). The magnetic tape head can thus record and read data along the length of the magnetic tape surface as relative movement occurs between the magnetic head and the tape.
In a magnetic disk drive system, a magnetic disk rotates at high speed while a magnetic head “flies” slightly above the surface of the rotating disk. The magnetic disk is typically rotated by means of a spindle drive motor.
Magnetoresistive (MR) sensors are particularly useful as read elements in magnetic heads, used in the data storage industry for high data recording densities. Three examples of MR materials used in the storage industry are anisotropic magnetoresistive (AMR), giant magnetoresistive (GMR) and tunneling magnetoresistive (TMR). An MR sensor is one whose resistance is changed by a magnetic field. MR, e.g., AMR, GMR and TMR, sensors are deposited as small and thin multi-layered sheet resistors on a structural substrate. The sheet resistors can be coupled to external devices by contact to metal pads which are electrically connected to the sheet resistors. MR sensors provide a high output signal which is not directly related to the head velocity as in the case of inductive read heads.
An important and continuing goal in the data storage industry is that of increasing the density of data stored on a medium recording medium. Efforts to achieve this goal may involve increasing the track and linear bit density on the magnetic recording medium. Additionally, efforts to achieve higher areal densities may also involve minimizing the spacing between the magnetic recording head(s) and the magnetic recording medium (i.e., the head-media spacing (HMS)). In particular, it is desirable to have the recording gaps of the transducers, which are the source of the magnetic recording flux, in near contact with the magnetic recording medium to effect writing sharp transitions, and to have the read elements in near contact with the magnetic recording medium to provide effective coupling of the magnetic field from the medium to the read elements. One further means of achieving high areal densities may involve fabrication of MR sensors with commensurately smaller dimensions.
However, the development of small footprint, higher performance magnetic storage systems is not without challenges. For instance, with reduced HMS and smaller sensor dimensions, the more sensitive the thin sheet resistors become to damage from spurious current or voltage spikes.
A major problem that is encountered during manufacturing, handling and use of MR sheet resistors as magnetic recording transducers is the buildup of electrostatic charges on the various elements of a head or other objects which come into contact with the sensors, particularly sensors of the thin film type, and the accompanying spurious discharge of the static electricity thus generated. Static charges may be externally produced and accumulate on instruments used by persons performing head manufacturing or testing function. These static charges may be discharged through the head, causing physical and/or magnetic damage to the sensors.
As described above, when a head is exposed to voltage or current inputs which are larger than that intended under normal operating conditions, the sensor and other parts of the head may be damaged. This sensitivity to electrical damage is particularly severe for MR read sensors because of their relatively small physical size. For example, an MR sensor used for high recording densities for magnetic tape media (on the order of 25 MBytes/cm2) are patterned as resistive sheets of MR and accompanying materials, and will have a combined thickness for the sensor sheets on the order of 500 Angstroms (Å) with a width of a few microns (μm) and a height on the order of 1 μm. Sensors used in extant disk drives are even smaller. Discharge currents of tens of milliamps through such a small resistor can cause severe damage or complete destruction of the MR sensor. The nature of the damage which may be experienced by an MR sensor varies significantly, including complete destruction of the sensor via melting and evaporation, oxidation of materials at the air bearing surface (ABS), generation of shorts via electrical breakdown, and milder forms of magnetic or physical damage in which the head performance may be degraded. Short time current or voltage pulses which cause extensive physical damage to a sensor are termed electrostatic discharge (ESD) pulses.
One major source of ESD damage is associated with tribocharging of the magnetic recording medium. Such tribocharging, which arises via frictional contact between the magnetic recording medium and the magnetic recording head, may lead to increased error rates and/or damage to the head, as discussed above.